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Successful Panoramic RadiographyA Peer-Reviewed Publication Edited by Dr. Robert A. Danforth

Go Green, Go Online to take your course

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Educational ObjectivesUpon completion of this course, the clinician will be able to do the following:1. Understand what constitutes a normal panoramic radio-

graph and the anatomical structures that can be identified on panoramic radiographs

2. Know the steps required to take a good panoramic radiograph and how to avoid errors

3. Understand the methods by which digital panoramic radiographs are captured, stored, retrieved and printed

4. Understand how to detect possible carotid artery calcifica-tions on panoramic radiographs

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AbstractThe panoramic radiograph continues to offer today’s dentist a unique patient view—covering the entire dentition and surrounding structures, the facial bones and condyles, and parts of the maxillary sinus and nasal complexes. The equip-ment used to obtain panoramic radiographs has continued to improve with recent advances, including automatic exposure and multiple image programs. However, achieving diagnostic panoramic images requires attention to the basic steps and correct patient positioning. This course will address the basic steps, problems, and errors that may occur when mistakes are made at any of these, allowing the practitioner to determine from the radiograph the point at which the error occurred in the image creation process. Once the error has been assessed, possible solutions to the problem are suggested. The result will be panoramic radiographs with the maximum diagnostic detail and information that the equipment and technique allow.

The Normal Panoramic RadiographBefore discussing various errors that can occur, it is important to know what a normal panoramic radiograph should look like. In a good panoramic radiograph the mandible is “U” shaped, the condyles are positioned about equal distance from the inside edges of the image and 1⁄3 of the way down from the top edge of the image. The occlusal plane exhibits a slight curve or “smile line,” upwards. The roots of the maxillary and mandibular anterior teeth are readily visible with minimal distortion. Mag-nification is equal on both sides of the midline (Figures 1, 3).

Panoramic TheoryWhy is panoramic radiography inherently technique sensi-tive? Panoramic radiography is a modified type of tomog-raphy or image layer radiography. The patient’s dental arch must be positioned within a narrow zone of sharp focus known as the “focal trough”/imaging plane (Figure 2), de-

signed by panoramic machine manufacturers as the ideal patient position to produce the optimum image. Distortion of the image quality occurs when patients are not properly positioned—such as if the chin is tipped up or down too much, midline rotated off machine center, anterior teeth/jaws too far forward or back. These result in vertical and horizontal magnification and distortion, superimposition of anatomical structures, and some structures being projected out of the field of view. In such cases, the interpretation of the resultant image is severely compromised.

These mistakes can only be remedied by a retake of the image with the patient in the proper position. This requires an additional patient exposure, further emphasizing the reason for following the patient alignment instructions provided by the system’s manufacturer.

Aside from radiation concern, the size of the focal trough/image plane is critical for a successful image. Machines are designed so that the focal trough/image plane is adjustable for patient size and programmed exposure parameters to coincide with the adjustments.

Older panoramic machine adjustments were more manual. Current machines are more automated. Preset icons represent-ing a range of large to small, or adult or child can be selected, automatically adjusting for arch width and focal trough/image plane size and the accompanying exposure factors. Many digi-tal machines also have automatic exposure control that vary the amount and energy of the X-rays during the actual exposure. Such automation facilitates imaging various size patients while reducing the potential of operator mistakes and assuring opti-mal patient dose.

Figure 2

Figure 1. Focal trough

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Patient PositioningMost panoramic machines offer positioning guides such as lights or plastic guides to position the patient along three major axes: anterior-posterior (too far forward or back), vertically (alartragus, Frankfort plane, or cantho-meatal lines), and mid-sagittal alignment (patient twisted or rotated).

Teeth and structures lying outside this zone of sharp focus will exhibit blurring, distortion or other artifacts. Therefore, all panoramic machines will have some mechanism for properly positioning the patient’s dentition within the focal trough. The trough on older systems can be as narrow as 3mm in width in the anterior region or as wide as 17mm on newer panoramic systems, therefore following the manufacturer’s guidelines for proper patient positioning is critical in obtaining a quality radiograph (Figure 4). As a general rule, the wider the anterior focal trough the easier it is to position the patient.

Proper patient positioning in the focal layer/plane of the panoramic machine is critical for producing successful images. Manufacturers have built into their machines a variety of align-ment devices to help ensure the patient positioning process is easy and well visualized by the dental operator.

Figures 5 and 6 show the typical alignment aids provided. The chin rest and the incisal guided bite-block assist position-ing the anterior teeth into the smallest region of the focal layer/plane. Lateral/temporal or frontal skull head support bars fur-

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1. Coronoid Process2. Sigmoid Notch3. Mandibular Condyle4. Condylar Neck5. Mandibular Ramus6. Angle of Mandible7. Inferior Border of Mandible8. Lingula9. Mandibular Canal10. Mastoid Process11. External Auditory Meatus

12. Glenoid Fossa13. Articular Eminence14. Zygomatic Arch15. Pterygoid Plates16. Pterygomaxillary Fissure17. Orbit18. Inferior Orbital Rim19. Infraorbital Canal20. Nasal Septum21. Inferior Turbinate22. Medial Wall of Max. Sinus

23. Inferior Border of Max. Sinus24. Posterolateral Wall of Max. Sinus25. Malar Process26. Hyoid Bone27. Cervical Vertebrae 1–428. Epiglottis29. Soft Tissues of Neck

(Look Vertically For Carotid Artery Calcifications Here)

30. Auricle31. Styloid Process

32. Oropharyngeal Air Space33. Nasal Air Space34. Mental Foramen35. Hard Palate

Figure 3

Figure 4. Positioning guides; note the bite rod, head guides, and aiming light

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ther assist posterior patient positioning and help to reduce head tilting and horizontal misalignment. Light beam reference lines provide the final visualization for proper patient alignment.

Light AlignmentLight alignment has three components: mid-sagittal head and skull plane, Frankfort plane, and canine/corner base of nose reference line.

The mid-sagittal line is an imaginary plane centered over the midline of the head which divides the anatomy into equal right and left sections when directed between the eyes along the midline of the nose and lips or between the maxil-lary central incisors, assuming the centrals are present and in an acceptable clinical position. This helps to ensure that the patient’s midline will be centered in the machine and prevents such errors as midline horizontal shift or sideways tilting of the head.1

The Frankfort plane line is used to position the patient’s head tilt in the vertical plane. The Frankfort plane is an external head reference plane which projects an imaginary line between the superior border of the external auditory meatus or upper portion of the tragus of the ear to the lower infraorbital rim of the eye. This plane is defined by a line between two anatomical external structures, the upper portion of the ear canal as identi-fied by the tragus and the lower border of the eye orbit, termed the infraorbital rim.2

Final forward/backward positioning of the patient’s head is determined using the canine/corner base of nose align-ment line. This is an imaginary, vertical line that primarily bisects the maxillary canine through the cusp and extends down through a portion of the mandibular canine. The head is moved forward or backward and adjusted until primar-ily the maxillary canine is bisected with the alignment line. This further ensures that the anterior teeth are in the narrow anterior portion of the focal layer/plane where proper posi-tioning is critical to prevent image distortion of the incisors. In newer systems there is no head movement, but rather the system adjusts the rotation to accomodate the patient’s bite. For patients that are edentulous in the regions of the canines, the base/alar corner of the nose can be used to achieve anterior jaw alignment.3

Image QualityMagnification and X-ray tube focal spot size are two impor-tant factors in determining extraoral image quality. Resolu-tion, the ability of an imaging system to produce distinct images of closely spaced objects, is an objective measure of image quality, and is expressed in units of Line Pair per mil-limeter (LP/mm). As the theoretical resolution increases, so does the system’s ability to reveal fine detail in the image (Figure 7).

The following chart (Figure 8), plots resolution versus magnification for four X-ray tube focal spot sizes. The area of interest is between 120 percent and 160 percent in magnification, typical of most panoramic and tomographic machines. The curves show conclusively that a smaller focal spot and minimal magnification will decrease blurring or image fuzziness.

Radiation DosageGenerally, intraoral digital radiography is touted as requir-

ing 70 percent to 90 percent less radiation than that for tradi-tional film radiography. Making such claims is not necessarily valid. The key to understanding these reductions is knowing what is being compared. The 70 percent to 90 percent reduc-tions compare to Ultra speed “D” film, the slowest film used in dentistry today. If comparison is made to faster “F” film, such reductions are negated and the exposure is in a similar range for digital radiography.

Patient size influences the amount of radiation necessary to produce a diagnostically useful radiographic image. Larger pa-tients require more radiation than smaller, meaning an increase or decrease in both the X-ray energy (kVp) and the amount of X-ray as determined by either the milleamperage (mA) and/or exposure time.

Recent studies comparing the effective patient dose for digital to conventional panoramic radiography have reported varied results. Reported effective doses for digital are 4.7µSv to 14.4, 5 µSv8,9 and 45µSv6. For conventional film panoramic radiography, effective values are 16–21 µSv2 and 54µSv.7 Results from Visser and Gijbels are similar and indicate a digital advantage ranging from a 13 percent to 77 percent reduction.8, 9 The actual dose values reported by Kiefer are greater than for the other studies but the digital advantage is within range at 17 percent reduction. Variations in study design and machines used for evaluation tend to produce wide ranging data, but overall, the results support the no-tion that digital imaging does reduce patient exposure for panoramic radiography.

The Basic StepsThere are several basic steps in taking a panoramic radiograph. These steps will apply to almost any panoramic machine, while some machines have features such as automatic exposure, which reduce the likelihood of exposure error, but do not prevent them entirely. It is important to know the steps and how they affect the outcome of the radiographic process. When problems occur at any of the steps they will cause unique errors on the resulting radiographs that when recognized, are easy to correct.1. Set exposure factors, if required.2. Have patient remove jewelry; place apron on patient’s back

and shoulders.3. Have patient bite on bite rod.4. Adjust the: a. chin tilt with the Frankfort light. b. head rotation with the mid-sagittal light. c. forward/backward head position with the

canine light.5. Position the side guides or head support.6. Have the patient stand up straight.7. Have patient swallow, place tongue on roof of mouth, and

hold still.8. Take X-ray

Figure 5 Figure 6

Small Focal Spot

Object

RecordingPlane

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Large Focal Spot

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RecordingPlane

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Small Focal Spot

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RecordingPlane

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Figure 8. Theoretical Maximum Resolution

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Figure 7. Magnification and X-ray tube focal spot size

To calculate the resolution for a given device, select the magnification, read vertically up the chart, until it intersects the focal spot line of the device. Read horizontally across the chart until it intersects the resolution axes. The intersection of these two lines will demonstrate the theoretical maximum resolution.

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Figure 9. Underexposure: note light, washed out image

Step 1: Setting Exposure Factors

Many newer panoramic machines set exposure factors automatically by measuring the amount of radiation passing through the patient’s head, or by measuring head width and adjusting exposure values accordingly. With some panoramic machines, though, exposure must be set based on the patient’s size or age. Usually, icons of small, medium, or large patients are used. Since the patient’s bone density is not always related to their physical size, a better guide is to look at the patient’s wrists or ankles. Thick wrists can imply heavier bone density; other factors to consider are age, whether the patient is edentulous, and obesity. Common exposure errors are illustrated in (Figure 9).

Problem Cause How to Correct Hints

Light, pale image with few dark areas Too little exposure Increase mA or kVp or use next

higher setting on machine Do not confuse with fogging (film), which is an overall grayness

Dark image with loss of details, amalgams and unex

posed areas are still clearToo much exposure Decrease machine settings

Step 2: Have Patient Remove Jewelry, Place Lead Apron on Patient

Prior to exposure, the patient must remove all jewelry from the head area. The panoramic exposure encompasses the whole head. Earrings, necklaces, or other jewelry, such as tongues bars or nose rings will be visible on the radiograph.

Problem Cause How to Correct Hints

White opacities on image; little or no image is visible Ghosts of metal jewelry Remove prior to exposure Watch out for necklaces

White opacity in palate Tongue bar Remove prior to exposure Image is projected high onto palate instead of floor of mouth

White opacity at bottom of image shaped like inverted “V”

or “shark fin”

Lead apron above collar line and in X-ray beam

Adjust and properly place apron

Watch for bunching at back of neck

Figure 10. Ghost of earring over left max sinus Figure 11. Tongue bar projected over palate Figure 12. Lead apron artifact

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Ghost Image“Ghost image” is a term used in panoramic radiography to de-scribe an image artifact produced when the shadow outline of a dense object on the side of the head toward the X-ray machine is projected across the image field and recorded on the film/image receptor on the opposite side of the head. This object’s outline becomes a radiopaque shadow artifact superimposed upon the structures of interest in the image field. This decreases image quality and can interfere with interpretation. “Ghost” images are easily identified as they are on the opposite side of the real image, higher on the film, and are streaked horizontally. They can be mistaken for pathology when they fall in the area of the sinus. Special panoramic aprons should be used that cover the back of the patient and the shoulder area. The apron must not extend above the collar or it will be imaged as an opaque “shark fin” artifact. This is due to the angle of the panoramic X-ray beam, which comes from below at approximately a seven- degree angle (Figures 10,11,12).

While normal anatomical structures such as the man-dibular ramus, hard palate, and spinal column can produce ghost image artifacts, the most recognized cause is patient earrings not removed during the examination. Although not much can be done to reduce the anatomical contribution to ghosting artifacts, removing patient jewelry will eliminate its contribution. The most common and annoying ghost artifact is that associated with the ramus/angle of the mandible which is persistently present over the second and third molar regions of the both the maxilla and mandible. Generally, this degrades interpretation of these areas, and when severe, makes inter-pretation impossible.

Figure 13 illustrates the projection factors associated with ghost image artifacts.

The colored rings in the skull views depict patient earring positions in relation to the X-ray machine and the film/image receptor. The divergent pathway of the primary X-ray beam to the image receptor is shown from both the right and left posi-tions to better convey that ghost artifacts generally affect both sides of the image. When the X-ray machine is positioned to the right side of the patient, it is actually the left side that is being imaged onto the film/image receptor. The path that the X-ray beam must travel to strike the film/image receptor is first through the right side entry anatomy, next across the entire skull

to enter the left side anatomy, and finally exit the patient to strike the film/image receptor, recording the left anatomy. The ghost image is always magnified and more superiorly positioned than the real object due to the projection distance across the skull and the angle of the X-ray beam inclined slightly upward.

Figure 14 is a panoramic image depicting double ghost earrings and the ghost affect of the ramus/angle of the man-dible superimposed upon the images of the maxillary and mandibular second and third molars. In this case, portions of the molars are not sufficiently seen for interpretation and a remake without earrings is indicated if other molar images are not available.

Digital Image Clarity and DefinitionA major advantage of digital radiography is it offers the pos-sibility to extract more information from the same image than ever achievable with film. Image enhancements allow optimization for whatever region of interest is being diagnosed. Images can be lightened or darkened in order to provide the optimum exposure. Higher resolution sensors can be magnified quite large in order to detect the tiniest abnormalities. Other image enhancements, such as local equalization, embossing, or colorization, improve the observer’s perception in order to aid in diagnosis.

Radiographic detail or definition measures the provided sharpness or clarity of an image in order to observe or vis-ibly differentiate between small objects that are in close proximity to one another. Digial panoramic system software allows you to zoom in on the image. Magnification can go to a 2:1 ratio and still be useful. Care must be taken not to over magnify the image as pixelization occurs and details become obscured. 10, 11

Enhancement tools such as brightness/contrast, invert and color have application upon the gray scale or color as-signment of pixel data. Selectively changing these influences visualization of certain data ranges over others. Contrast and brightness may help to visualize caries detection in enamel and yet obscure the fine trabecular pattern of the alveolar bone. Invert enhancement seems to favor visualization of periodontal structures yet not caries detection. Color has not been shown to have any specific clinical relevance not capable of being seen by the other tools.12, 13

Figure 13 Figure 14

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Step 3: Bite on Rod

Most panoramic machines use a bite rod made of plastic with small grooves to position the patient’s anterior teeth in the focal trough. Most machines also offer an edentulous guide that is placed against the patient’s chin or under the nose. These guides are also useful in partially edentulous cases as well, and failure to use them can cause anterior-posterior errors. Other causes of patients being too far forward or back in the focal trough are anterior malocclusions such as bimaxillary protrusion. Most machines offer a correction for these cases. Many machines offer an aiming device centered on the mandibular cuspid, as it is considered to be more indicative of the patient’s skeletal position (Figures 15,16).

Problem Cause How to Correct Hints

Anterior teeth blurry, too small and narrow, spine visible on

sides of image

Patient biting too far forward on bite rod

Make sure anterior teeth are located in grooves on rod

Make sure mandibular incisors are in groove also, and bite rod

is not being bent forward

Anterior teeth blurry and wide, ghosting of mandible and spine, condyles close to edge of image

Patient is biting too far back on rod or not at all

Make sure anterior teeth are located in grooves on rod

If anterior teeth are missing use edentulous guide

Figure 15. Patient too far forward; note spine superimposed over rami, blurring, and narrowing of anterior teeth

Figure 16. Patient too far back; note ghosting of mandible and spine, condyles pushed to outside of film, blurring and widening of anterior teeth

Step 4: Adjust Chin Tilt

In the panoramic radiograph the patient should be looking slightly down at a spot on the floor approximately 8 feet in front of them. This elevates the posterior palate so it does not overlap the apices of the maxillary teeth in the final image. This is often referred to as “chin tilt.” Having the patient’s chin tipped too far down is the most common panoramic error (Figures 17,18).

Problem Cause How to Correct Hints

Roots of lower incisors blurry, mandible shaped like a “V”,

too much smile line, condyles at top of image, spine forms arch

or “gazebo” effect

Patient’s chin is tipped too far down

Reposition using proper guidelines for that machine,

such as alar-tragus line

Make sure patient does not have unusual occlusal

plane orientation

Maxillary incisors blurry, hard palate superimposed on roots, flat occlusal plane, mandible is broad and flat, condyles at edge

of image

Patient’s chin is tipped too far up

Reposition using proper guidelines for that machine

such as alar-tragus line

Make sure bite rod remains seated in its guide

Figure 17. Chin tipped down; note V-shaped mandible, extreme smile line, arching of spine at top of image, condyles placed high on film, and streaking of the hyoid bone over the mandible

Figure 18. Chin up too high; note flattened occlusal plane, palate superimposed on max-illary tooth roots, and broad flat mandible

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Step 5: Position and Close Side Guides

All panoramic machines will have guides or positioning lights to align the patient’s midsagittal plane. It is important that the patient be looking straight ahead with no tip or tilt to the head. Side guides or head and temple supports may be used and may come from either the top or the bottom of the machine. When the patient’s head is twisted, it is similar to being too far forward on one side and too far back on the other (Figure 19).

Problem Cause How to Correct Hints

Teeth are wide on one side, narrow on other; ramus is wider on one side than the other; uneven pattern of

blurring throughout arch; nasal structures not clear

Patient’s head is twisted in machine causing midline asymmetry

Reposition using proper guidelines for that machine

Make sure patient doesn’t try and look towards technician, but straight ahead. Always use front-surface mirror on machine to check alignment

Condyles are not equal in height,

nasal structures distorted

Patient’s head is rotated in machine (tipped)

Reposition using proper guidelines for that machine

Make sure patient’s head remains level through ears

Step 6: Have Patient Stand Up Straight

The patient must be standing up straight to prevent arching of the neck (slumping). The best method of achieving this is not to allow the patient to reach forward to the bite stick or chin rest. Have the patient take a step forward after they are biting on the rod. They should feel somewhat as if they will fall backward if they let go of the hand-holds. This will avoid problems with the system hitting the shoulders and spinal ghosting (Figure 20).

Problem Cause How to Correct Hints

White tapered opacity in middle of image

Ghost of spinal column due to slumping

Have patient take a step forward and straighten neck

Do not allow patient to reach forward into machine; make

them step forward

Figure 20. Slumped; note the white spine shadow in midline

Figure 19. Head twisted; note uneven width of rami, unequal magnification of teeth, and condyles

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Storing Digital ImagesOnce the digital image is captured in the computer, it is ready for electronic storage, printing, or digital transfer. Generally, digital images are initially stored in the pa-tient file on the computer’s hard drive, or preferably on a separate server or other file method so as not to overload the computer storage capacity. File size, method of trans-fer, image quality, and legal aspects of the image should be considered.

Captured images can be stored in imaging management program, or by transfer to any other compatible third-party treatment planning program. Network systems have server file systems for storage from which practice management systems image viewing programs can access the image files for viewing along with other patient data.

Printing And Viewing

Digital ImagesWhen printing or electronically transferring an image from stor-age, various file format options are available; common formats include the following: tif, jpeg, bmp, and pdf. When printing hard copies, any of these file formats and various others can be used. Size of the file and print quality must be decided by the individual user and may be influenced by the reason for printing the image. Generally, there is an increase in file size and print-ing time with increased desired print quality. Efficient prints intended for emails and clinical reference images are generally done in the jpeg format with standard printing parameters.

Most jpeg images are associated with a “Lossy” compres-sion format that reduces file size to a better manageable volume,

Step 7: Have Patient Swallow, Place Tongue in Roof of Mouth, and Hold Still

Just before the exposure is made, the patient is instructed to swallow, place the tongue on the roof of the mouth, and hold still during the exposure. Failure to do these things can result in patient movement artifacts or airway obscuring vital portions of the image. In particular, not placing the tongue in the roof of the mouth results in a large airway shadow directly over the roots of the maxillary teeth (Figures 21,22).

Step 8: Exposure

Problems during exposure are primarily due to machine or operator errors including letting go of exposure button temporarily (not possible with most recent machines), changing exposure settings during the exposure.

Problem Cause How to Correct Hints

White vertical line on image running from top to bottom

edge of image

Exposure stopped briefly, probably due to letting go

of exposure button

Hold exposure button down firmly during exposure

Modern machines will return to start position if this happens

This completes the basic steps for panoramic radiography.

Figure 21. Tongue down during exposure; note shadow of air space over roots of maxillary molars, airway space over rami

Figure 22. Patient movement; note step defect in inferior border of mandible

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making printing and electronic transfer more efficient. The drawback to this compression is that data is discarded or lost to make the file smaller. This may result in an image that may no longer be considered a legal representation of the patient, as would a traditional film radiograph. For practical use, this has little relevance to clinical practice but would most likely not withstand legal scrutiny. Similar considerations exist for images transferred to CDs, although the “read only” feature does limit alteration of images burned to that specific CD.

Another file format designed for image transfer and main-tenance of image integrity is DICOM—Digital Imaging and Communications in Medicine—and is the standard format for distributing and viewing medical images regardless of the image capture source or the end users software viewing programs. This format is becoming more widely used in den-tistry as electronic transfer of dental image data becomes more common. Teleradiology implies that all image data will be transferred or used electronically with little dependence upon any form of hard copies or data disk transfers. This concept is already a reality, and the DICOM format will help to assure image integrity.

What Do I Do if a Digital Image Is Captured and Stored in the Wrong Patient File?One of the advantages of digital radiography is assignment of the digital image into the appropriate patient’s electronic record. The process begins with establishing an electronic record for a new patient or recalling a previous record for patients already entered into the system.

For the new patient, once all identification of data has been entered, the selection for the type of radiographic examination can be made. The processing computer acknowledges this selection and prepares to accept the incoming data from the image receptor. Upon reception of the image, the computer displays the image on the monitor for visual evaluation. The

image has been “tagged” with the appropriate electronic file codes to specifically match the patient of record, date, and type of radiographic image.

To make radiographic images for a recorded patient, the patient’s file is identified and brought onto the monitor screen. At this point proper identification of the patient is critical to avoid potential image storage mistakes.

Although the first instinct if an image has been capture and stored in the wrong patient file may be to find the correct file and remake the image, this should be discouraged as the patient will have to inappropriately endure another radiation exposure. Copied images can be exported or imported from the incorrect file to the correct one, but they will be renamed and labeled with another transfer format (i.e., jpeg, bmp, or tif), as the new file cannot accept an original captured image from another file. Image export and import choices are found under the list of image management options. The copied image format label will signify that the image is not an original captured image for that file; this is not clinically important if proper identification and reason for copied image transfer have been properly docu-mented in the correct record.

Generally, images that have been incorrectly made in the wrong patient file can be deleted, preferably after copy transfer to the correct record. If not, then appropriate documentation of the incorrect image is mandatory to avoid confusion.

Carotid Artery Calcifications On Panoramic RadiographsThe annual number of strokes in the United States is about 730,000 with approximately 23 percent being fatal. Approxi-mately one-half of strokes are believed to be associated with emboli that originate from artherosclerotic plaque calcifications located in the bifurcation region of the external and internal carotid arteries. Screening methods that provide detection of such calcifications can potentially save lives.

Figure 23A Figure 23B

Figure 23C Figure 23D

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Several studies have shown how panoramic radiography can play a role in detection. The bifurcation of the internal and external carotid arteries lies in a panoramic imaging plane ap-proximately 1.5cm to 2.5cm posterior and inferior to the man-dibular angle in the darken space primarily anterior to cervical spine C4 and slightly inferior to the posterior horn of the hyoid bone (Figures 23A–C). Although the actual carotid arteries cannot be seen, the presence of vertical-linear nodular opacities in the prevertebral space extending anterior along C3, C4, and sometimes C5 is suggestive for artherosclerotic plaques in the vessel walls (Figures 23B–D).14,15

Making such a panoramic interpretation must be tempered with caution. Adequately visualizing the anterior portions of C3 and C4 is critical for interpretation. In some film images, the area is darken and detection is difficult without increasing the viewing light intensity. With digital panoramic radiography, such areas can be enhanced with brightness/contrast or sharp-ening adjustments (Figure 23D). Also, several other opacities can be seen in and around this area than could mimic carotid calcifications. A differential interpretation of these would in-clude the posterior portion of the hyoid, upper portion of the thyroid cartilage, epiglottis, triticeous cartilage, and possible calcified lymph nodes or other vessels.

If interpretative confidence of carotid calcifications is suf-ficient after differentiating the other possibilities, the patient should be informed to have further evaluation done by their physician. Such an evaluation will, most likely, included ultra-sound testing for a more definitive diagnosis.16

Although panoramic imaging is not a precise screening method for detection of carotid artery calcifications, it is a supplemental aid that dentists should be aware of when inter-preting panoramic images.

ConclusionPanoramic radiography provides the dentist with an image of the whole dentition and adjacent structures. While panoramic radiography is technique sensitive, by carefully following the ten steps outlined, clear and undistorted radiographs of high di-agnostic quality can be consistently obtained. In today’s digital age, capturing and storing panoramic radiographs is a reliable procedure that if combined with practice management software enables the patient’s image to be recalled together with his file when needed.

References1 Langland,OE and Langlais,RP. Principles of dental imaging,

Williams & Wilkins, 1st ed. 1997; 207–275.2 Ibid.3 Ibid.4 Visser H, Hermann KP, Bredemeier S, and Kohler B. Dose

measurements comparing conventional and digital panoramic radiography. Mund Kiefer Gesichtschir. 2000: Jul; 4(4) 231–16.

5 Gijbels F, Jacobs R and et al. Dosimetery of digital panoramic imaging. Part I: Patient exposure. Dentomaxillofac Radiol. 2005 May; 34(3):150–3.

6 Kiefer H, Lambrecht JT, Roth J. Dose exposure from analog and digital full mouth radiography and panoramic radiography. Schweiz Monatsschr Zahnmed. 2000;114(7):687–93.

7 Ibid.8 Visser H, Hermann KP, Bredemeier S, and Kohler B. Dose

measurements comparing conventional and digital panoramic radiography. Mund Kiefer Gesichtschir. 2000: Jul;4(4) 231–16.

9 Gijbels F, Jacobs R and et al. Dosimetery of digital panoramic imaging. Part I: Patient exposure. Dentomaxillofac Radiol. 2005 May; 34(3):150–3.

10 Kodak RVG 5000 Digital Radiography System Users guide topic — “Using the full resolution” Eastman Kodak Company, 2004

11 Going Digital: The Digital X-ray Guidebook to Success, Chapter 4: Electronic Image Processing (electronic vs. chemical) Dentrix Dental Systems, 2004

12 Kodak RVG 5000 Digital Radiography System Users guide, topic — “Using the full resolution” Eastman Kodak Company, 2004

13 Going Digital: The Digital X-ray Guidebook to Success, Chapter 4: Electronic Image Processing (electronic vs. chemical) Dentrix Dental Systems, 2004

14 Almog DM and et al. Case Report: Unrecognized carotid artery stenosis discovered by calcifications on a panoramic radiograph. JADA, 2000;131: 1953–54.

15 Farman AG. Panoramic radiology and the detection of carotid atherosclerosis. Panoramic imaging news 2001;1(2):1–16Almog DM, and et al. Correlating carotid artery stenosis detected by panoramic radiography with clinical relevant carotid artery stenosis determined by duplex ultrasound. Oral surg Oral Med Oral Path Oral Radiol Endod. 2002;94:768–73.

16 Almog DM, and et al. Correlating carotid artery stenosis detected by panoramic radiography with clinical relevant carotid artery stenosis determined by duplex ultrasound. Oral surg Oral Med Oral Path Oral Radiol Endod. 2002;94:768–73.

Editor ProfileDr. Robert A. Danforth is a board certified oral pathologist whose career has generally been directed toward oral radiol-ogy education. He has taught dental radiography since 1979 in three dental schools and has been involved with the dental radiography laboratory service since 1984. He first introduced intraoral and panoramic digital radiography into his oral ra-diology teaching courses in 1999 and, in addition, has given multiple continuing education courses on digital imaging. He was the contributing editor for the California Dental As-sociation Journal December 1999. “New Millennium” issue, which completely featured digital Oral and Maxillofacial imaging as the new age in dentistry. Later, he had the same opportunity, again for the California Dental Association Journal, November 2003 issue to introduce 3D Cone Beam Computed Tomography (CBCT) as the next innovative imag-ing modality for dentistry.

DisclaimerThe author of this course has no commercial ties with the spon-sors or the providers of the unrestricted educational grant for this course.

Reader FeedbackWe encourage your comments on this or any PennWell course. For your convenience, an online feedback form is available at www.ineedce.com.

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Questions

1. The area of sharp focus in panoramic radiography is known as the:a. Exposure zoneb. Focal troughc. Aiming grooved. Tomographic zone

2. In digital panoramic radiography, the narrow anterior focal trough is:a. Doubled in sizeb. Measured by the computerc. Remains the samed. Of no importance

3. A panoramic radiograph shows the mandible to be V-shaped and narrowed with the condyles high on the film. The occlusal curve is exaggerated and the spine arches over top of the film. The patient’s head tilt was most likely pointing _____.a. Too highb. Too lowc. Tippedd. Twisted

4. A large tapered vertical radiopacity in the center of the panoramic radiography is usu-ally caused by the ghost of the spine due to:a. Patient is too far back in the machineb. Patient’s head tilted too far upc. Patient was slumping, neck was curvedd. Patient’s head was twisted

5. When the patient is properly positioned in the panoramic machine, they should feel:a. Very comfortableb. Nervousc. Like they will fall backwards if they let go of

the handholdsd. Like they are leaning forward

6. If the Frontal/Image Layer plane were positioned incorrectly, which of the follow-ing errors would occur?a. Patient positioned too far back or forwardb. Patient positioned too far up or downc. Patient positioned too far left or rightd. All of the above

7. A white inverted V-shaped radiopacity on the bottom of the film is most likely caused by:a. Ghosts of metal jewelryb. Ghost of hyoid bone c. Lead apron artifactd. Damaged cassette

8. A panoramic radiograph shows small, nar-rowed anterior teeth with the spine visible on both sides of the film. The patient was probably positioned ______on the bite rod.a. Too far forward b. Too far backc. Too highd. Too low

9. Calcification of the carotid artery usually appears on an image in what location:a. Soft tissues of the neckb. Mandibular canalc. Medial wall of maxillary sinusd. Mental foramen

10. “Ghost” images are caused by:a. Metal jewelryb. Position of patient’s chin tipped too far upc. X-ray beam alignmentd. None of the above

11. For referral to another doctor, a digital image can be:a. Printedb. Copied to a CDc. Sent by E-maild. All of the above

12. If a digital image is made (captured) in an incorrect patient’s file, what is the best way to correct it?a. Move it to the correct patient’s fileb. Retake another image in the correct

patient’s filec. Nothing. It will remain in the original filed. Copy image, but the original will stay in the

other patient’s file

13. Before making a digital panoramic image, the computer attached to the X-ray unit should:a. Have the patient’s name on the screenb. Be idle, to save screen lifec. Be connected to a printerd. Have a network connection

14. A poorly positioned digital radiograph can be corrected by:a. Using brightness and contrast toolsb. Using the magnifying tool to enlarge imagec. Using the color toolsd. None of the above

15. As a general rule, the wider the anterior trough: a. The easier it is to position the patientb. The less comfortable the patient will bec. The darker the image will bed. None of the above

16. X-ray images can be stored on the computer in which program:a. Imaging program from X-ray sourceb. Imaging program from Practice Managementc. Imaging program from any 3rd party dental or

treatment/planning specialty programd. Any of the above

17. When taking a panoramic radiograph on a 7 year old child, which best describes the proper technique to follow:a. Adjust the X-ray unit up or down b. Turn the X-ray unit off and on, to clear the

previous settingsc. Make sure the X-ray unit is set for pedo

settings, instead of adult settingsd. Make sure the patient is seated on a chair

or stool

18.To show small anatomical detail, the best tool to use is:a. Colorb. Invertc. Magnifyd. Brightness/Contrast

19. When considering the Frankfort plane, which part of the patient does this plane focus on?a. Upper canine, or base of the nose, if edentulousb. Center of the nose and chinc. Ear opening and infraorbital notchd. Carotid artery area

20. When considering the Mid-sagittal plane, which part of the patient does this plane focus on?a. Upper canine, or base of the nose, if edentulousb. Center of the lip and chinc. Ear opening and infraorbital notchd. All of the above

21. When considering the Frontal/Image Layer plane, which part of the patient does this plane focus on?a. Upper canine, or base of the nose, if edentulousb. Center of the lip and chinc. Ear opening and infraorbital notchd. None of the above

22. If the Frankfort plane were positioned incorrectly, which of the following errors would occur?a. Patient positioned too far back or forwardb. Patient positioned too far up or downc. Patient positioned too far left or rightd. Patient’s head at an angle

23. If the Mid-sagittal plane were positioned incorrectly, which of the following errors would occur?a. Patient positioned too far back or forwardb. Patient positioned too far up or downc. Patient positioned too far left or rightd. All of the above

24. The final visualization for proper patient alignment is provided by:a. Light beam reference linesb. Transecting threads on either side of

the patientc. A digital imaging grid used prior to taking

the radiographd. None of the above

25. Automatic exposure control facilitates:a. Imaging various patient sizesb. The prevention of ghostingc. Reduction of operator mistakesd. a and c

26. The Frankfort plane is used to: a. Position the patient’s chin heightb. Position the patient’s head tilt in the

vertical planec. Position the patient’s head tilt in the

sagittal planed. None of the above

27. For patients who are edentulous in the canine region, the _______________ can be used to achieve anterior jaw alignment:a. Imaginary line running horizontally from the

tips of the patient’s earlobesb. Tip of the nose and chinc. Base/alar corner of the nosed. All of the above

28. To improve the observer’s perception, digital image enhancement can be achieved by:a. Local equalizationb. Colorizationc. Embossingd. All of the above

29. The components of light alignment are:a. Mid-sagittal head and skull planeb. Canine/corner base of nose reference linec. Frankfort planed. All of the above

30. A large airway shadow directly over the roots of the maxillary teeth occurs due to: a. Air in the nasal passages and sinusb. The patient not placing the tongue in the roof

of the mouth while the image is being takenc. a and bd. None of the above

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ANSWER SHEET

Successful Panoramic Radiography

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Requirements for successful completion of the course and to obtain dental continuing education credits: 1) Read the entire course. 2) Complete all information above. 3) Complete answer sheets in either pen or pencil. 4) Mark only one answer for each question. 5) A score of 70% on this test will earn you 4 CE credits. 6) Complete the Course Evaluation below. 7) Make check payable to PennWell Corp.

Educational Objectives1. Understand what constitutes a normal panoramic radiograph and the anatomical structures that can be identified on

panoramic radiographs

2. Know the steps required to take a good panoramic radiograph and how to avoid errors

3. Understand the methods by which digital panoramic radiographs are captured, stored, retrieved and printed

4. Understand how to detect possible carotid artery calcifications on panoramic radiographs

Course EvaluationPlease evaluate this course by responding to the following statements, using a scale of Excellent = 5 to Poor = 0.

1. Were the individual course objectives met? Objective #1: Yes No Objective #3: Yes No

Objective #2: Yes No Objective #4: Yes No

2. To what extent were the course objectives accomplished overall? 5 4 3 2 1 0

3. Please rate your personal mastery of the course objectives. 5 4 3 2 1 0

4. How would you rate the objectives and educational methods? 5 4 3 2 1 0

5. How do you rate the author’s grasp of the topic? 5 4 3 2 1 0

6. Please rate the instructor’s effectiveness. 5 4 3 2 1 0

7. Was the overall administration of the course effective? 5 4 3 2 1 0

8. Do you feel that the references were adequate? Yes No

9. Would you participate in a similar program on a different topic? Yes No

10. If any of the continuing education questions were unclear or ambiguous, please list them.

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11. Was there any subject matter you found confusing? Please describe.

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12. What additional continuing dental education topics would you like to see?

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AUTHOR DISCLAIMERThe author of this course has no commercial ties with the sponsors or the providers of the unrestricted educational grant for this course.

SPONSOR/PROVIDERThis course was made possible through an unrestricted educational grant. No manufacturer or third party has had any input into the development of course content. All content has been derived from references listed, and or the opinions of clinicians. Please direct all questions pertaining to PennWell or the administration of this course to Machele Galloway, 1421 S. Sheridan Rd., Tulsa, OK 74112 or macheleg@pennwell.com.

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Completing a single continuing education course does not provide enough information to give the participant the feeling that s/he is an expert in the field related to the course topic. It is a combination of many educational courses and clinical experience that allows the participant to develop skills and expertise.

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